1. Field of the Invention
The present invention relates to an electric motor and a fan.
2. Description of the Related Art
Motors have been used as driving sources for a variety of electronic devices. A spindle motor of a hard disk drive disclosed in JP-A 9-210054 includes a rotor assembly and a stator assembly. The stator assembly includes a frame, a fixed shaft, and a ring-shaped thrust plate. The fixed shaft is arranged to stand upright in a central portion of the frame. The thrust plate is fixed to an upper portion of the fixed shaft. Thrust dynamic pressure bearing portions are defined in both axial end surfaces of the thrust plate. The rotor assembly includes a hub, a cylindrical radial dynamic pressure bearing portion, and a thrust support plate. The radial dynamic pressure bearing portion is arranged in a central portion of the hub. The fixed shaft is inserted in the radial dynamic pressure bearing portion. The thrust plate is arranged on an upper side of the radial dynamic pressure bearing portion. The thrust support plate is screwed onto the hub on an upper side of the thrust plate.
During rotation of the hub, the hub is supported in a radial direction through a dynamic pressure generated by a lubricant in a gap defined between the radial dynamic pressure bearing portion and the fixed shaft. In addition, the hub is supported in an axial direction through dynamic pressures generated by the lubricant in a gap defined between the thrust plate and the radial dynamic pressure bearing portion, and a gap defined between the thrust plate and the thrust support plate. Capillary seal portions are defined in a lower portion of the gap defined between the radial dynamic pressure bearing portion and the fixed shaft, and a gap defined between the fixed shaft and the thrust support plate.